Hydrogen cyanide is highly toxic. It is a known attack agent in chemical warfare. It is also a very important chemical for use in numerous industrial processes. Its salts, e.g., sodium cyanide and potassium cyanide are also used in many industrial processes and also are highly toxic.
When cyanide intoxication is experienced, the cyanide interferes with the performance of the cytochrome oxidase system thereby inhibiting the efficiency of oxygen transport to the tissues. Therapeutic attempts to counteract cyanide poisoning have largely consisted of the introduction of compounds such as the nitrites like sodium nitrite. More recently, dimethylaminophenol has been used in order to produce methemoglobin. As a result of cyanide's greater affinity for methemoglobin than for the cytochrome oxidase system, it leaves the latter and forms cyanomethemoglobin thereby restoring, at least partially, the oxygen transport function of the cytochrome oxidase system. Subsequently therapy with thiosulfate, e.g., sodium thiosulfate, converts the cyanide to thiocyanate which is then excreted by the kidney.
For the effective treatment of cyanide poisoning, it is important that hemoglobin be rapidly converted to methemoglobin. It is also important that the effect of the treatment be long lasting, e.g., 30 to 60 minutes or even longer. While sodium nitrite has been successfully used, as indicated supra, it has the disadvantage that it is relatively slow in converting hemoglobin to methemoglobin.
Dimethylaminophenol very rapidly converts hemoglobin to methemoglobin but has the disadvantage that it is relatively expensive, the intramuscular injection hurts, causes an abscess and may be difficult to stabilize in an appropriate injector.
It has long been known that hydroxylamine and hydroxylamine hydrochloride cause methemoglobinemia, e.g., see J. Boil. Chem., Vol. 143, 331 (1942) and Merck Index, 8th and 9th Edition. However, no one has shown that hydroxylamine or hydroxylamine hydrochloride could be used as a therapeutic drug to counteract cyanide poisoning.